If you're making a character that is starting with a Devil Fruit, then you can make the character or the Devil Fruit in whichever order you like. However, you must get the Devil Fruit accepted before the character can be accepted. Or I believe that's how it is anyway.

All the fruits in the advanced section are considered custom, even canon ones. This allows users to expand upon the existing canon fruits that have had little screen time with users that were far from mastering them. Therefore all fruits must be made, even those that are canon.

As long as the fruit isn't in the character's profile the character can be approved before the fruit. However in-order to use the fruit it and the character must first be approved.